Ten LeVeen shunts were inserted into nine patients with intractable ascites and coagulation studies were performed to determine the incidence, severity, and clinical importance of disseminated intravascular coagulation (DIC) in the initial post-operative period. Two of the shunts failed to function in the immediate post-operative period and the clotting profiles of these patients were unchanged by surgery. The remaining shunts had good initial flow and in all patients there was a deterioration in the coagulation profile consistent with DIC. In four of these patients this was associated with clinical evidence of impaired haemostasis which required surgical ligation of the shunt in two as an emergency measure. The other two patients died as a direct consequence of their bleeding. Of the eight initially patent shunts, one blocked spontaneously and three others were surgically ligated in the early post-operative period. The clotting abnormalities of all of these patients returned to pre-operative levels with the cessation of flow through the shunts. Four patients had continued shunt patency during their hospital stay and, in all, titres of fibrin degradation products remained elevated. The conclusions reached are that adequate flow through the peritoneovenous shunt causes laboratory evidence of DIC in all patients and this can be of major clinical importance; that monitoring of the coagulation profile is a good index of continued shunt patency at least in the early post-operative period; and that DIC may account for the high spontaneous blockage rate.